JPH10293054A - Flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flowmeter for accurately measuring the fluid flow rate of, for example, a gas within a wide flop-rate range. SOLUTION: A measurement region 15 for a small flow rate and a measurement region 16 for a large flow rate are provided in a channel 13 of a pipe 10. A rectification strainer 14 as a rectification member for rectifying the flow of a gas 20 is provided at the measurement region 15 for a small flow rate. The straightening strainer 14 is divided into a plurality of small channels 14A with a smaller sectional area than the channel 13 of the measurement region 16 for a large flow rate by a partition wall, and the gas 20 flows through a plurality of small channels 14A. In the measurement region 15 for a small flow rate, flow-rate sensors 15a and 15b for a small flow rate being provided on the wall surface of the pipe 10 output a signal according to the flow rate of the flow-rate sensor 15 for a small flow rate being provided on the wall surface of the pipe 10. At the measurement region 16 for a large flow rate, the flow-rate sensors 16a and 16b for a large flow rate output a signal according to the flow rate of the gas 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow meter for measuring a flow rate of a fluid such as a gas, and more particularly to a flow meter capable of accurately measuring a flow rate in a wide flow rate range.

[0002]

2. Description of the Related Art FIG. 5 shows a specific structure of a conventional flow meter. One flow rate sensor 1 is disposed at the center of a fluid flow path in a pipe 2, and a flow rate calculating section 3 controls a flow rate. Sensor 1
Is multiplied by the cross-sectional area of the pipe 2 to calculate the flow rate, and the flow rate is displayed on the display unit 4. Here, in order to maintain high accuracy of the flow rate measurement by the flow rate sensor, the flow rate sensor 1 needs to be arranged in the most stable flow of the fluid.

[0003]

However, in the conventional flowmeter, there is a problem that it is difficult to determine the mounting position of the flow velocity sensor 1 because a drift occurs in the pipe 2 depending on the flow rate. In addition, it is necessary to install the flow velocity sensor 1 only in a flow rate range with a small deviation, so that the measurement range of the flow rate becomes narrow, and there is a problem that the gas flow rate cannot be measured accurately in a wide flow rate range.

[0004] As a household gas meter, in addition to the function of measuring the flow rate of gas passing therethrough, one equipped with a microcomputer and added with a safety function has been put into practical use. When the pressure is detected or when a predetermined gas flow rate is detected for a predetermined time or more, the gas shutoff valve is driven to shut off the gas flow path. These functions detect leaks in pipes and unnatural gas leaks, prevent accidents before they occur, and ensure safety.To ensure that such functions operate correctly, Therefore, accurate measurement of the gas flow rate in a wide flow rate range is desired.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a flow meter capable of accurately measuring the flow rate of a fluid such as gas in a wide flow rate range.

[0006]

A flow meter according to the present invention has a flow path through which a fluid passes, and a measurement area for a small flow rate and a measurement area for a large flow rate are provided along the longitudinal direction of the flow path. Pipe, a rectifying member provided in the small flow rate measurement area in the flow path of the pipe and forming a plurality of small flow paths having a smaller cross-sectional area than the flow path, and an inner wall surface of the pipe in the large flow rate measurement area And a first flow rate sensor that outputs a signal corresponding to the flow velocity of the fluid passing through the large flow rate measurement area, and a first flow rate sensor that is provided on the inner wall surface of the pipe in the large flow rate measurement area and formed by a rectifying member. A second flow rate sensor that outputs a signal corresponding to the flow rate of the fluid passing through the small flow path; and at least one of an output signal of the first flow rate sensor and an output signal of the second flow rate sensor according to the flow rate. Calculate flow based on And a quantity calculation means.

In this flowmeter, in the large flow rate measurement area, a signal corresponding to the flow velocity of the fluid passing through this area is output from the first flow rate sensor. On the other hand, in the small flow rate measurement region, a signal corresponding to the flow rate of the fluid passing through the small flow path formed by the rectifying member is output from the second flow rate sensor. The flow rate calculating means calculates the flow rate based on at least one of the output signal of the first flow rate sensor and the output signal of the second flow rate sensor according to the flow rate.

According to a second aspect of the present invention, there is provided a flow meter according to the first aspect, wherein a plurality of second flow rate sensors are provided on the inner wall surface of the pipe at positions facing the small flow paths. An average flow velocity in the small flow rate measurement area is calculated based on the output signal of the sensor, and the average flow velocity in the small flow rate measurement area is output to the flow rate calculation means.

In this flow meter, the average value of the flow velocity in the measurement area for small flow rate is calculated from the output signals of the plurality of second flow rate sensors, and the flow rate calculation means calculates the flow rate based on the average flow rate value.

According to a third aspect of the present invention, there is provided a flow meter according to the second aspect, wherein a plurality of first flow rate sensors are provided on the inner wall surface of the pipe at positions facing the small flow paths. The apparatus is further provided with an average flow velocity calculating means in the large flow rate measurement area which calculates an average value of the flow velocity in the large flow rate measurement area from the output signal of the sensor and outputs the average value to the flow rate calculation means.

In this flow meter, the average value of the flow velocity in the large flow rate measurement area is calculated from the output signals of the plurality of first flow velocity sensors, and the flow rate calculating means calculates the large flow rate measurement area based on the average flow velocity value. Is calculated.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing a configuration of a flow meter according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. The flow meter according to the present embodiment is used as a gas meter. The flow meter 10A includes a pipe 10 having an inlet 11 for receiving the gas 20 and an outlet 12 for discharging the gas 20. The diameter of the flow path 13 in the pipe 10 is, for example, 50 mm. A measurement area 15 for a small flow rate and a measurement area 16 for a large flow rate are provided in the flow path 13 along the longitudinal direction. A rectification strainer 14 as a rectification member for adjusting the flow of the gas 20 is provided in the small flow rate measurement area 15.

As shown in FIG. 2, the rectifying strainer 14 is divided by a partition wall into a plurality of small flow paths 14A having a smaller cross-sectional area than the flow path 13 in the large flow rate measurement area 16. The gas 20 flows through the small channel 14A. Corresponding to the small flow path 14A, small flow velocity sensor insertion portions 17a and 17b are provided in the pipe 10 at positions facing each other (up and down positions in the figure). Small flow rate sensors 15a and 15b are attached. That is, the detection units of the small flow rate sensors 15a and 15b are formed by a plurality of small flow paths 14 formed by the rectifying strainers 14.
A faces the center of the small flow path 14A closest to the wall surface. The upstream and downstream sides of the straightening strainer 14 are, for example, a wire mesh 19 of about # 100 mesh.
a and 19b are provided.

In the measurement area 16 for large flow, the pipe 1
At 0, large flow velocity sensor insertion sections 18a and 18b are provided at positions facing each other (up and down positions in the figure), and large flow velocity sensor sections 16a and 16b are attached to these large flow velocity sensor insertion sections 18a and 18b. Have been.

FIGS. 3A and 3B are for explaining the difference in the flow velocity distribution depending on the presence or absence of the rectifying strainer 14. FIG. 3A shows the rectifying strainer 14 as in this embodiment. Flow velocity distribution 30 when installed, FIG. 3 (b)
Is the flow velocity distribution 31 in the channel 13 without the rectifying strainer.
Respectively. Generally, the flow velocity distribution is the fastest at the center of each flow path and becomes slower as it approaches the wall. Therefore, as shown in FIG.
When the flow rate sensor 4 is not provided, there is a gap between the small flow rate sensors 15a and 15b mounted on the wall surface and the peak portion of the flow rate distribution 31 (that is, the center of the flow path 13). In 15a and 15b, the flow velocity of a relatively low flow velocity part in the flow velocity distribution 31 is measured. On the other hand, in the present embodiment, a plurality of small channels 14A are formed by the rectifying strainer 14, and each small channel 1A is formed.
There is a flow velocity distribution 30 every 4A. Therefore, the peak portion of the flow velocity distribution 30 (that is, the central portion of the small flow path 14A) and the pipe 1
The measurement sensitivity is high because the distance from the zero wall surface is short and the detection units of the small flow rate sensors 15a and 15b attached to the wall surface are located at the positions corresponding to the peaks of the flow velocity distribution 30.

The small flow rate sensors 15a, 15b
Although not shown, the large flow velocity sensors 16a and 16b have a heat generating portion and two temperature sensors disposed on the upstream and downstream sides of the heat generating portion, and have a temperature detected by the two temperature sensors. The flow rate corresponding to the flow velocity is obtained from the power supplied to the heat generating section necessary to keep the difference constant, or the heat generating section is heated with a constant current or constant power, and the flow rate is calculated from the difference between the temperatures detected by the two temperature sensors. You can ask for it.

FIG. 4 is a block diagram showing a configuration of a circuit portion of the flow meter 10A according to the present embodiment. Flow meter 10A
Is a small flow path 1 formed by the rectifying strainer 14 based on each output signal of the small flow rate flow rate sensors 15a and 15b.
Average flow velocity calculating unit 41 for calculating the average value of the flow velocity in 4A
An average flow velocity calculator 42 for calculating an average value of the flow velocity in the large flow measurement area 16 based on the output signals of the large flow velocity sensors 16a and 16b, and an output of the average flow velocity calculator 41 according to the flow rate. And a signal switching unit 43 for selecting and outputting one of the outputs of the average flow velocity calculating unit 42, a display unit 45 for displaying the flow rate and the integrated flow rate based on the output of the signal switching unit 43, and a flow rate calculating unit 44. Output terminal 46 for outputting the measured flow rate and the integrated flow rate to the outside
And When the flow rate calculated by the flow rate calculation section 44 is within the preset small flow rate range, the signal switching section 43 outputs the output of the average flow rate calculation section 41 to the flow rate calculation section 44 and is calculated by the flow rate calculation section 44. When the flow rate is in a preset large flow rate range, the output of the average flow velocity calculation section 42 is output to the flow rate calculation section 44. When the flow rate is in a predetermined small flow rate range, the flow rate calculation unit 44 multiplies the average value of the flow velocity output from the average flow velocity calculation unit 41 by a pipe shape coefficient corresponding to the small flow path 14A in the rectification strainer 14. When the flow rate is in a preset large flow rate range, the flow rate 13 is output to the average value of the flow rate, which is the output of the average flow rate calculation unit 42, in the flow path 13 downstream of the rectifying strainer 14.
The flow rate is calculated by multiplying by the pipe shape coefficient corresponding to.

When the flow rate increases by partially overlapping the small flow rate area and the large flow rate area, when the flow rate reaches the upper limit of the overlapping area, the average flow rate calculation unit 41 calculates the average flow rate. The output is switched to the output of the section 42, and when the flow rate decreases, the flow rate is calculated by switching from the output of the average flow rate calculating section 42 to the output of the average flow rate calculating section 41 when the flow rate reaches the lower limit value of the overlapping area. May be. Average flow velocity calculator 4
The reference numerals 1 and 42, the signal switching unit 43, and the flow rate calculation unit 44 can be constituted by, for example, a microcomputer.

Next, the operation of the flow meter 10A according to the present embodiment will be described.

The gas 20 introduced from the inlet 11
First, in the small flow rate measurement area 15, each of the small flow paths 14 </ b> A in the straightening strainer 14 passes.
At this time, the small flow velocity sensors 15a and 15b provided on the wall surface of the flow path 13 output a signal corresponding to the flow velocity of the gas 20 passing through the small flow path 14A. The gas 20 that has passed through the small flow rate measurement area 15 passes through the large flow rate measurement area 16 and is discharged from the outlet 12. At this time, the large flow rate sensors 16a and 16b output a signal corresponding to the flow rate of the gas 20 passing through the large flow rate measurement region 16.

The average flow velocity calculating section 41 includes a rectifying strainer 1
Flow rate sensor 15 for small flow rate in small flow path 14A in
The average value of the flow velocity in the small flow path 14A is calculated based on the output signals a and 15b.
a, a large flow rate measurement area 1 based on the output signals of 16b
The average value of the flow velocity in 6 is calculated. Signal switching unit 43
Outputs the output of the average flow velocity calculating section 41 to the flow rate calculating section 44 when the flow rate calculated by the flow rate calculating section 44 is in the preset small flow rate range, and the flow rate calculated by the flow rate calculating section 44 is set in advance. When the current flow rate is in the large flow rate range, the output of the average flow velocity calculation section 42 is output to the flow rate calculation section 44. When the flow rate is within a predetermined small flow rate range, the flow rate calculation unit 44 calculates the flow rate and the integrated flow rate based on the average value of the flow velocity output from the average flow velocity calculation unit 41, and sets the flow rate to a predetermined large flow rate. When in the flow rate range, the average flow velocity calculation unit 4
The flow rate and the integrated flow rate are calculated based on the average value of the flow velocity which is the output of 2. The integrated flow rate calculated by the flow rate calculation unit 44 is displayed on the display unit 45. The small flow rate region and the large flow rate region are partially overlapped, and in the overlap region, the flow rate calculated based on the average value of the flow velocity output from the flow rate calculation unit 44 and the average flow rate calculation unit 41 and the average flow rate calculation unit 42 An average value with the flow rate calculated based on the average value of the flow velocity, which is the output of, may be obtained, and this average value may be used as the measured flow rate.

In this embodiment, the flow rate sensor 1 for a small flow rate is used.
5a and 15b are attached to the plane of the pipe 10, and the flow rate sensors 15a and 15b for small flow rate face the small flow path 14A divided by the rectifying strainer 14, respectively, and the detection units of the flow rate sensors 15a and 15b for small flow rate are small. Channel 14A
Because it is located at the center of the inside, accurate and highly sensitive measurement can be performed without being affected by the disturbance of the flow of the gas 20. In the present embodiment, the flow rate sensors 15a and 15b for small flow rate and the flow rate sensors 16a and 16a for large flow rate
Since 16b can be directly attached to the pipe 10,
The connection between the measurement device main body including the average flow velocity calculation units 41 and 42 and the flow rate calculation unit 44 can be facilitated. When the flow rate sensors 15a and 15b for small flow rate and the flow rate sensors 16a and 16b for large flow rate are abnormal, the flow path 13
Maintenance can be performed without disassembling the whole.

Although the present invention has been described with reference to the embodiment, the present invention is not limited to the above embodiment, and can be variously modified. For example, in the above embodiment, two small flow rate flow sensors 15a and 15b and two large flow rate flow sensors 16a and 16b are provided, but these numbers are arbitrary. However, when a plurality of flow velocity sensors are provided, even if an abnormality occurs in one flow velocity sensor, measurement can be performed by another flow velocity sensor. Therefore, in terms of reliability, the number of each flow velocity sensor is two or more. It is desirable to do.

Also, the large flow rate measurement region 16 is located on the upstream side,
The measurement area 15 for small flow rates may be formed on the downstream side. Further, the cross-sectional shape of the flow path 13 is not limited to a circle, but may be a semicircle, an ellipse,
The shape may be a square or the like. Further, the flow velocity sensor is not limited to the one having the heat generating portion and the two temperature sensors,
For example, it has one heat-generating part, determines the flow velocity from the power supplied to the heat-generating part necessary to keep the temperature (resistance) of the heat-generating part constant, or heats the heat-generating part with a constant current or constant power to generate heat. The flow rate may be obtained from the temperature (resistance) of the section. Further, the present invention can be applied to a flow meter that measures the flow rate of not only gas but also gas and liquid as well as gas.

[0026]

As described above, according to the flowmeter of the first aspect, in the small flow rate measurement area, a plurality of small flow paths are formed by the rectifying member, and the piping is arranged so as to face the small flow paths. Since the second flow velocity sensor is provided on the wall surface of, the flow rate can be measured with high accuracy without being affected by the drift of the fluid in the small flow rate measurement area. Further, since it is not necessary to install the second flow rate sensor in a flow rate range with a small drift, the measurement range of the flow rate is expanded.
In addition, since the second flow rate sensor is mounted on the wall surface of the pipe, there is an effect that the mounting operation and the response to the abnormality of the second flow rate sensor are facilitated.

In particular, according to the flow meter of the present invention, since a plurality of second flow velocity sensors are installed and the average value of the output of each flow velocity sensor is used as the measurement result, the measurement accuracy is improved and When an abnormality occurs in one of the second flow velocity sensors, the flow rate can be measured by another second flow velocity sensor in which no abnormality has occurred, so that there is an effect that reliability is improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of a flow meter according to an embodiment of the present invention.

FIG. 2 is AA for explaining the straightening strainer of FIG. 1;
It is sectional drawing of the direction of the arrow of a line.

FIG. 3 is a diagram for explaining a basic principle of the present invention;
FIG. 4A shows the flow velocity distribution in the flow path when the flow straightening strainer is installed in the flow meter, and FIG. 4B shows the flow velocity distribution in the flow path when the flow straightening strainer is not installed in the flow meter. FIG.

FIG. 4 is a block diagram illustrating a circuit configuration of the flow meter of FIG.

FIG. 5 is a cross-sectional view illustrating a configuration of a conventional flow meter.

[Explanation of symbols]

Reference Signs List 10A flow meter 10 piping 11 inlet 12 outlet 13 flow path 14 rectifying strainer (rectifying member) 14A small flow path 15 measurement area for small flow rate 15a, 15b flow rate sensor for small flow rate (second flow rate sensor) 16 for large flow rate Measurement area 16a, 16b Flow rate sensor for large flow rate (first flow rate sensor) 17a, 17b Flow rate sensor insertion section for small flow rate 18a, 18b Flow rate sensor insertion section for large flow rate 19a, 19b Wire mesh 20 Gas

Claims (3)

[Claims] 1. A pipe having a flow path through which a fluid passes and provided with a small flow rate measurement area and a large flow rate measurement area along a longitudinal direction of the flow path; A rectifying member provided in the flow rate measurement area and forming a plurality of small flow paths having a smaller cross-sectional area than the flow path, and provided on the inner wall surface of the pipe in the large flow rate measurement area, and a large flow rate measurement area A first flow rate sensor that outputs a signal corresponding to the flow rate of the passing fluid, and a flow rate of the fluid that is provided on the inner wall surface of the pipe in the large flow rate measurement area and passes through the small flow path formed by the rectifying member. A second flow rate sensor that outputs a signal corresponding to the flow rate, and a flow rate calculation that calculates a flow rate based on at least one of the output signal of the first flow rate sensor and the output signal of the second flow rate sensor in accordance with the flow rate Means Flowmeter and said that there were pictures. 2. A plurality of second flow rate sensors are provided on the inner wall surface of the pipe at positions facing small flow paths, and the output signals of the plurality of second flow rate sensors determine the flow rate in a small flow rate measurement area. 2. The flowmeter according to claim 1, further comprising an average flow velocity calculating means of a small flow rate measurement area for calculating an average value and outputting the calculated average value to the flow rate calculating means. 3. A plurality of the first flow rate sensors are provided at positions facing the small flow path on the inner wall surface of the pipe, and the output signals of the plurality of first flow rate sensors determine the flow rate in the large flow rate measurement area. 3. The flowmeter according to claim 2, further comprising an average flow velocity calculating means for calculating a large flow rate in the measurement area for a large flow rate which calculates an average value and outputs the calculated average value to the flow rate calculating means.